The Paris Climate Agreement is signed by national governments. But mayors and regional leaders are increasingly taking the lead in implementing measures to keep global warming below 2 degrees Celsius.
At the forefront of this effort is an alliance of cities, states and businesses from the United States. After President Donald Trump announced in June he would withdraw the US from the Paris Climate Agreement, mayors, governors, university professors and CEOs from across the country have publicly confirmed their commitment to the international climate deal.
At the UN climate conference in Bonn, the coalition under the banner America's Pledge: We Are Still In has published a report outlining the scale of their action to fulfil the goals set out under Paris Climate Agreement: to reduce emissions by 26-28 percent below 2005 levels by 2025.
Although these alternative US climate commitments are not part of the Paris Agreement, former New York City Mayor Michael Bloomberg, who is spearheading the America's Pledge initiative together with California's Governor Jerry Brown, says he hopes the international community accepts their pledge alongside the nationally determined contributions of other countries.
"In Paris, the US pledged to measure and report our progress reducing emissions," Bloomberg said speaking at the summit in Bonn. "Through America's Pledge, we're doing just that, and we're going to continue to uphold our end of the deal, with or without Washington."
The cities, states and businesses participating in the initiative represent more than half of the US economy and population. If this group were a country, it would be the third largest economy in the world — and the fourth largest polluter.
The international community at COP23 has welcomed the pledge. "This initiative shows that the campaign for climate action in America remains strong," Fiji's Prime Minister Frank Bainimarama said, speaking in his role as president of this year's UN climate summit.
"I also hope that it is a model that can be followed elsewhere in the world," he added. "The governments alone can't do all the things necessary to beat climate change. We need everyone."
Cities are important players
Local and regional leaders in the US aren't the only ones stepping up to the fight against climate change. Mayors from every continent of the world have gathered in Bonn to exchange ideas and best practices to reduce greenhouse gas emissions.
Cities have a key role to play in meeting the Paris climate goals, experts say. Urban areas are responsible for 70 percent of global greenhouse gas emissions from fossil fuels used for energy and transport.
More than half of the global population lives in cities. By 2050, two out of three people could be calling a city home. Considering this development, mayors acknowledge it's time to reinvent metropolises as resilient, low-carbon societies.
Celestine Ketcha Courtes, mayor of the town of Bangagte in Cameroon, says there’s no time to lose. "We are growing fast. In the coming years, Africa will triple while the rest of the world will double," she said at a press conference at the summit, referring the rapidly growing global population. "That's why we need to work now on sustainable solutions."
While national governments introduce laws and regulations to fight climate change, it should be mayors who take the lead in transforming cities, Courtes argues. "They know best what works on the ground and what not."